Problems with light due to installation

Hi when I turn my system full on then you can see in front of the headlights that they don’t get the right juice (flattening at the bass) you told me that in my car a continuous current cable is missing so that I can also install it myself have one that makes me 30 euro or is that due to something else ???? Have an audio 80 b4 bj 12/92 90 ps